Quenched amplifier system



1386- 1948- R. c. MOORE QUENCHED AMPLIFIER SYSTEM Filed Aug. 2, 1944 93 h, a M I? fiw Patented Dec. 21, 1948 QUENCHED AMPLIFIER SYSTEM Robert C. Moore, Philadelphia, Pa., a'ssignor, by mesne assignments, to Philco Corporation, Philadelphia, Pa., a corporationof Pennsylvania Application August 2, 1944, Serial No. 547,720

This invention relates to quenched amplifier systems and particularly to quenched amplifying systems in which the duration of the quenching 'period is adjustable.

In some applications of amplifying systems; it is desirable to employ an amplifier which isnonresponsive to incoming signals for some predetermined interval after the response to a desired signal. For example, this characteristic is particularly desirable in pulse-actuated amplifiers employed to initiate certain events in other parts of an electronic system. For example, such amplifiers may be employed to trigger wave shaping circuits, timing pulse generators, oscillator circuits, or the like. circuit may complete the desired operation initiated by a pulse signal, it is desirable to prevent any subsequent incoming signals from interfering with this desired operation of the triggered circuits. means may be provided to place the input signal amplifying system in an inoperative condition for an interval of time approximately equal to the time required for the triggered circuit to complete its desired function. After completion of the desired events in the triggered circuit, the input signal amplifier may be returned to its normal condition ready to respond to another pulse signal.

Furthermore, it is desirable that the inoperative or protection period of the input signal amplifying system be easily varied between limits in order to accommodate any desired changes in the operating period of the triggered circuit.

The principal object of this invention is to provide a high efiicient quenching system for a pulse-responsive amplifier.

Another object of the invention to provide a quenching system in which the quenching period is readily adjustable,

A further object of the invention is to provide a quenching system employing a single-cycle oscillatory circuit, e. g. a multivibrator, to effect the quenching action.

Other objects and advantages of the present invention will become apparent during the course of the following description with reference to the accompanying drawing, in which Fig. 1 is a diagrammatic illustration of an embodiment of the invention; and

Fig. 2 is an explanatory illustration of the operation of the system.

Referring first to Fig. I, there'is shown a pulse amplifying circuit, comprising vacuum tubes T1 and T2 and their respective circuit elements,

In order that the triggered To accomplish this protection, some 7 Claims. (o1.250-2 7) capacitively coupled to 2 a quenching circuit comprising vacuum tubes T3 and T4 arranged in a modified common cathode loaded multivibrator circuit. As will be seen later, the multivibrator is adapted for single cycle operation, i. e. it opcrates only for a single cycle when triggered by an applied potential. While separate triodes are shown in the drawing; it is to be understood that duplex type tubes may be used, and other multielectrode tubes may be substituted for the triodes, utilizing the appropriate circuit modifications.

In accordance with the embodiment of the invention shown in the drawing, vacuum tube T1 is arranged in conventional amplifier fashion, with an input circuit comprising coupling condenser I0 and grid resistor H, and a plate load with zero grid'bias'f The output of tube T1 is applied in a conventional manner, by means of coupling condenser l4 and grid resistor IE, to the grid of the self-biased cathode loaded amplifier tube T2. Resistor It with by-pass condenser [1 forms a conventional self-biasing means for the grid of tube T2. The bias on the grid of this tube should preferably be such that tube T2 is operated approximately'at cut-ofi. Resistor l8 in the cathode circuit of tube T2 is the cathode load resistor across which the output signal of the amplifier is developed. The anode potential for tube T2 is derived from tap I9 on a voltage divider 20 connected across a; suitable anode voltage source B+. A bypass condenser 2| is connected between tap l9 and ground. The potential at tap l9 is applied to the plate of tube -T2 through the tuned circuit 22 which is designed to be resonant at a frequency such that the time 'tube T3.

The common cathode connection of tubes T3 and T4 is grounded through a common load resistance composed of resistors 25 and 26 in series.

It is to'be understood. that a single tapped resistor may be used in place of the two resistors 25 and 26. The, anodes of tubes Taand T4 are con- 3 nected through resistors 28 and 29 respectively to the anode voltage source B The plate of tube T3 is coupled to the grid of tube T4 by means of coupling condenser 30. The grid of tube Ta is connected through grid resistor 21 to the junction of resistors 25 and 26. The grid of tube T3 is therefore biased by the voltage drop developed across resistor 25 due'to platepurrentssof tubes T3 andT i flowingthrough this resistor: The circuit constants of tubes T3 and T4 are so chosen that the plate current of tube T4 is greater than that of tube T3 thereby biasing tubetTs. beyond cut-off during the time tube T4 is conducting.

The grid of tube T4 is connected to the commonii cathode connection of tubes Taand Tifitln rough the total resistance of fixed resistor 31 'i'n-series Movable contactwith a variable resistance 3-2; arm 33 permits adjustment in the value of the input circuit resistance of tube T4.

The operation of the;. system will now be explained' with. reference .to the; explanatory -zillus1- v tration of Fig. 2..

With the 1 system,- in" La. .=.normal-..condition;t;that

is, ready to receive-anegative-pulsev atxinputa terminal 34, vacuun'rtubes. T1,: andfTicsare-conductv- 'ing. As-previouslyw-statedi';tube Tt. is-biasedapthe output terminal 35;; Thereisalsodeveloped by the resonant'circuit 22 .asnegat'ive signal volt-- age 1 (curve e Ti of Flg;t2')' onrthesplaterof; tube Tz'at. the instant the negative-input pulseris applied; Since I the time of :one *half. cyolerofv the oscillating voltagensetnup in:-.tuned-. circuit 22 is equal to: the duration: timeeaof the applied; pulse the signal voltage on -.the raplate: :Ofl rtubeTa :will begin togopositive: at the end-off the appliediptulse. This positive signal. voltage onthe-pl'ate- 'of tube T2, duetoathevtrans'ient oscillating voltage-set upinrresonant. circuit :22, is "applied through acoupling condenser '24-'to the-grid of. tube; 1T3; thereby raising, itsv potential abovethe-zcut-ofi value. At this instant the quenching..-circuit.-. regenerates,

that is; tube T3 becomesconductingiand :tubeT4 is cut-off duetothe negative fpotentialaapplied to its grid: from the plate r of .tube 5T3 by means "of coupling:condenser:=30;. Seecurvesi Tyandi Tr of Fig.2..

Now sincevthe plate current vof tube- T4. :has -been=cut-of and sinceitheeplatecurrent nfaxitube T3: is muchvless. thanwthew: conduction :ourrent. of tube -T4, thapotentiar (ease-4114): or :thecommon cathode. connection issso reduced that/theaplate voltage -isbpractically! removedfrom 'the-input tube T1 of the'amplifier, as shown by curve qesTi of Fig. 2. This" drop. inpotential of c the *plate of tube Tris applied to the 'grid of tube T2 through condenser !4 and places the grid of tube Tawellbe- Thus, with tin-exceedinglylowiplate. voltageion tubeTi and-the grid of tube "Tz' Well. beyond cutoff, theamplifier is non-responsive to incoming signals.

The system will remain"imthis wndi i t n ll i l' vide .an. impulse which initiatesoperation of. the

.output. pulse.

condenser 30 has discharged sufliciently, through resistors 3| and 32, to bring the potential on the grid of tube T4 up to its cut-ofi value, at which time the quenching system will again regenerate in multivibrator fashion to cause tube T4 to conduct and thereby restore the system to its normal condition ready to respond again to another negative pulse; In Fig. 2, thetime "during which the amplifier is quenched is represented by time interval T.

The length of time the amplifier is insensitive depends upon. the time that tube T4 remains in a non-conducting state. This interval is controlled by" the time. constant of the resistance-capacitance inputscircuit of tube T4, which comprises condenser 30 and the total resistance of fixed resistor 3!. and variable resistor 32. Adjustment of the setting of movable contact arm 33 varies the time constant of the input circuit of tube T4 thereby permitting variation in the quenching-interval. of :the system.

Itwill. be realized by. those skilled. in theartv that in:order .to maintain the-grid of the secondamplifier tube T2 well below cut-off.;during; the :quenchingsperiod-thetimeconstant of the condenser- .transient alternatingavoltagessetup in. tuned circuit .22. is quickly attenuated:

From the foregoing description, .itv will be. seen thattubes .Ts and-T4 and-theirassociated elements format single-cycle multivibrator .whoseperiod of operation is .controllableby means .of variable resistor 32., and..means areprovided. to effect quenching ,of- .the. amplifier ..during .the operation of. the .multivib-rator- In. the embodiment of ..the..invention..as illus- .tnated, the .resonant. circuit. .22 jislutilized to .pro-

oscillatory circuit. comprising. .tubes T3 and T4 Without. interfering with. the amplification .of .the input, pulse. and .the derivation. ofthe amplified However, .the initiation of operation of. the said oscillatory ,circuitmay be accom- .plished..in .any other suitable. manner without usingthe resonant. circuit 22. Foreexample,v the output pulse appearing at terminal 35.may be .applied. to a suitable pulse-forming, circuitv whose output pulse may then be applie'dito .tubeTl by wayof the coup-ling condenser 24. Variousmethads. of accomplishing the desired operation .will be apparent to those skilled in the art.

In practicing this invention in-accordance with thaembodiment shown in the drawing, with. a 250 volt anode potential-source and with vacuum tubes. T1 and T2 each. a section of type INT-and tubes T3 and T4 each a. section of a. type 7N7, the circuit elements were as follows;

micro-microfarads; 500 Condensers "i 4 sand I L-" microfarads 04005 Condenser 2| do 01 Resistors 'and'Z'L ohms 4705000 Resistor l2." ..-d'o 6,800 Resistors I 5, l 8, '28 and 32 megohms 1 Resistor l8. ohms 2,200 Resistor 20". do 218,000 Resistors 23 and'29 do 22-,000 Resistors Hand 26. do 3900 Resistor 3I' do 68,000 Inductance l3 m'illihenrys 1 The-inductance and capacity of 'tunedcircuit 22 was 2 millihenrys and'100 micro-microfarads respectively. The tap IS on voltage divider 20 was at a position 68,000 ohms from the grounded end of the voltage divider.

Although the present invention has been described with particular referenceto the embodiment shown in the drawing, it will be understood that the invention is capable of various forms of physical expression and is limited only by the scope of the appended claims.

I claim:

1. In combination, a pulse-responsive amplifier comprising an input tube having an anode and a cathode loaded output tube having an anode circuit, a single-cycle multivibrator coupled to the anode circuit of said output tube, a resonant circuit in the anode circuit of said output tube for producing a transient potential capable of triggering said multivibrator, and means responsive to operation of said multivibrator for reducing the anode potential of said input tube so as to render said amplifier substantially inoperable during the operation of the multivibrator.

2. In combination, a pulse-responsive amplifier including an input tube having an anode, a single-cycle multivibrator including a first tube coupled to said amplifier and a second tube coupled to said first tube, said multivibrator tubes having anodes and having a common cathode circuit including an impedance across which a voltage is produced by the anode current of said tubes, means for applying said voltage to the anode of said input tube, said multivibrator being so constructed and arranged that its first tube is normally non-conductive and its second tube is normally conductive and the amplitude of said voltage is normally sufficient to maintain operation of said input tube but becomes insuflicient to maintain such operation when the multivibrator operates, and means operable by said amplifier in response to a pulse signal for initiating operation of said multivibrator, whereby the amplifier is quenched for a predetermined period corresponding to the period of operation of the multivibrator.

3. In combination, a pulse-responsive amplifier including an input tube having an anode and a cathode loaded output tube having an anode circuit, a single-cycle multivibrator including a first tube coupled to the anode circuit of said output tube and a second tube coupled to said first tube, said multivibrator tubes having anodes and having a common cathode circuit including an impedance across which a voltage is produced by the anode current of said tubes, means for applying said voltage to the anode of said input tube, said multivibrator being so constructed and arranged that its first tube is normally nonconductive and its second tube is normally conductive, and the amplitude of said voltage is normally sufiicient to maintain operation of said input tube but becomes insufiicient to maintain such operation when the multivibrator operates, and means in the anode circuit of said output tube for producing a transient potential in response to a pulse signal thus initiating operation of said multivibrator, whereby the amplifier is quenched for a predetermined period corresponding to the period of operation of the multivibrator.

4. In combination, a pulse-responsive amplifier including an input tube having an anode and a cathode loaded output tube having an anode circuit, a single-cycle multivibrator including a first tube coupled to the anode circuit of said output tube and a second tube coupled to said first tube, said multivibrator tubes having anodes and having a common cathode circuit including an impedance across which a voltage is produced by the anode current of said tubes, means for applying said voltages to the anode of said input tube, said multivibrator being so constructed and arranged that its first tube is normally non-conductive and its second tube is normally conductive, and the amplitude of said voltage is normally sufi'icient to maintain operation of said input tube but becomes insumci-ent to maintain such operation when the multivibrator operates, and a resonant circuit in the anode circuit of said output tube for producing a transient potential in response to a pulse signal thus initiating operation of said multivibrator, whereby the amplifier is quenched for a predetermined period corresponding to the period of operation of the multivibrator.

5. In combination, a pulse-responsive amplifier including an input tube having an anode and a cathode loaded out-put tube, :a normally-inoperative electron tube device adapted to operate for a predetermined period in response to a triggering potential applied thereto, means operable by said amplifier in response to a pulse signal for triggering said device, and means responsive to operation of said device for reducing the anode potential of said input tube and for simultaneously biasing said output tube below cut-01f, so as to render said amplifier substantially inoperable during the operation of said device.

6. In combination, a pulse-responsive amplifier, a trigger-type device characterized in that it is adapted to produce a relatively long pulse of predetermined duration in response to a short triggering pulse, means for triggering said device in response to a short pulse supplied to said amplifier, said triggering means comprising a resonant circuit arranged to be shocl -excited by the operation of said amplifier and to apply a transient triggering pulse to said device, and means controlled by said device for rendering said amplifier substantially inoperable during the occurrence of said long pulse, whereby said device functions to quench said amplifier for a predetermined time interval following said short pulse, said time interval corresponding to the duration of said long pulse.

'7. In combination, a pulse-responsive amplifier comprising an input tube having an anode and a cathode-loaded output tube having an anode circuit, a trigger-type device characterized in that it is adapted to produce a relatively long pulse of predetermined duration in response to a short triggering pulse, means connected in the anode circuit of said output tube for triggering said device in response to a short pulse supplied to said amplifier, said triggering means comprising a resonant circuit arranged to be shock-excited by the operation of said "amplifier and to apply a transient triggering pulse to said device, and means controlled by said device for reducing the anode potential of said input tube to render said amplifier substantially inoperable during the occurrence of said long pulse, whereby said device functions to quench said amplifier for a predetermined time interval following said short pulse, said time interval corresponding to the duration of said long pulse.

ROBERT C. MOORE.

(References on following page) REFERENCES CITED The following references are of record ir1 the file of this patent:

Nu be UNITED STATES PATENTS Name Date Kramar June 18, 1938 Andrieu et a1 Mar. 19, 1940 Kotowski et 'al. Dec, 3, 1940 Blumlein Dec. 10, 1940 Schonland Dec. 9, 1941 Sonnentag et a1. Jan. 20, 1942 Number i Name Date Koch Mar. 3,1942 Bingley Mar. 27, 1942 Michel July 13, 1943 Atwood Aug. 12, 1947 FOREIGN PATENTS Country Date Great Britain Aug. 24, 1, 31 Great Britain Feb; 14, 1938 Great Britain Feb. 24, 1938 

